Unfortunately for the vast majority of applications the economics don't work to use flywheels. The possible exceptions are applications that cycle a million or more times (capturing and returning energy from subway train stops, extreme grid stability issues).
Power density of flywheels is a little better than lead acid batteries, but the energy density is much worse.
Tracy is correct, the parasitic losses are high. And Dave is correct, no one will want a 60,000rpm flywheel in their truck when they can have a non moving lithium ion battery.
We developed flywheels for transportation and stationary applications in the 1990s, but the lithium ion battery came in and proved a much better solution.
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Brian Jensen
brian@jensenenergyresearch.com------------------------------
Original Message:
Sent: Sep 10, 2021 10:26 AM
From: Dave Erb
Subject: Energy storage - Battery v. Flywheel
Harmon -
Flywheels can store a lot of energy, but they're not without their challenges. Efficiency concerns dictate very close attention to friction reduction schemes, like maglev bearings and evacuated containers, and the competing technologies (batteries, capacitors, pumped storage hydro) set the bar pretty high. Lower-speed flywheels are heavy. Lightweight flywheels have to spin extremely fast (dentist drill speeds) to store much energy, which makes any structural failure catastrophic.
In vehicles, crash safety is a very big deal, and precession forces aren't trivial (they're usually addressed by putting two counter-rotating flywheels in one container). Speaking as an automotive engineer with 40 years experience in energy and emissions development, there are a few reasons to consider flywheels in terrestrial vehicular applications, but a whole lot more reasons not to. I suspect my colleagues in the utility and off-grid world would say the same.
Hope this helps. Best,
Dave Erb
Original Message:
Sent: 9/9/2021 9:35:00 PM
From: Harmon Lookhoff
Subject: Energy storage - Battery v. Flywheel
I know very llitle about this but Irecall that very high amounts of energy (momentum) can be st;ored on flywheels, very large heavy disks that spin at high rpm, on axles supported on ball bearings, in an enclosed container (do not want this thing to fly apart out in the open) and the container is air evacuated to near vacuum. Very little friction loss. How could this be used? Stationary Vehicles. I know not from whence I speak; I am a lawyer, not an engineer. I would like to hear any thoughts on this.